System and method for positron emission tomography

ABSTRACT

A method and system for using in a Positron Emission Tomography (PET) system. The PET system comprises at least one processor and a storage. The PET system comprises an acquisition module and a processing module. The acquisition module is configured to acquire a PET data set corresponding to a target object. The acquisition module comprises a first light sensor array, a second light sensor array, and a scintillator array. The processing module is configured to determine a three-dimensional position of an incidence photon based on the PET data set. The first number of light sensors in the first light sensor array and the second number of light sensors of the second light sensor array is less than the number of scintillator of the scintillator array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application is a continuation of U.S. patent applicationSer. No. 15/692,163, filed on Aug. 31, 2017, which is a continuation ofInternational Application No. PCT/CN2017/091093, filed on Jun. 30, 2017,designating the United States of America, the contents of each of whichare hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to a medical system, and morespecifically relates to methods and systems for determining athree-dimensional position of an incidence photon in a positron emissiontomography (PET), and/or single photon emission computed tomography(SPECT).

BACKGROUND

PET and SPECT imaging devices operate by sensing incidence photons(e.g., gamma photons) emitted by radiopharmaceuticals that have beenaccumulated in target organs or tissues of a patient. A two-dimensionalor three-dimensional image is constructed based on positions ofparticular annihilation events. The positions of particular annihilationevents may be determined based on positions of incidence photonscorresponding to the particular annihilation events. There is a need fora system and a method for determining the positions of incidence photonsmore accurately.

SUMMARY

The present disclosure relates to a Positron Emission Tomography (PET)system. One aspect of the present disclosure relates to the PET systemcomprising at least one processor and a storage. The PET system maycomprise an acquisition module and a processing module. The acquisitionmodule may comprise a first light sensor array, a second light sensorarray, and a scintillator array. The acquisition module may beconfigured to acquire a PET data set corresponding to a target object.The first light sensor array may be optically coupled to a first surfaceof the scintillator array. The second light sensor array may beoptically coupled to a second surface of the scintillator array. A firstnumber of the light sensors in the first light sensor array may be lessthan a number of scintillator elements in the scintillator array. Asecond number of the second light sensor array may be less than a numberof scintillator elements in the scintillator array.

In some embodiments, the PET system may further comprise a processingmodule. The processing module may be configured to determine thethree-dimensional position of the incidence photon based on the PET dataset.

In some embodiments, at least one light sensor in the first light sensorarray or the second light sensor array may comprise a siliconphotomultiplier (SiPM).

In some embodiments, an image reconstruction unit may be configured toreconstruct an image of the target object based on the three-dimensionalposition of the incidence photon and the PET data set.

In some embodiments, at least one component of the three-dimensionalposition of the incidence photon in a direction may be determined basedon a light intensity spatial distribution corresponding to the incidencephoton in the direction.

In some embodiments, the PET data set may comprise a first data setcomprising at least a first light intensity value corresponding to theincidence photon detected by the first light sensor array, and a seconddata set may comprise at least a second light intensity valuecorresponding to the incidence photon detected by the second sensorarray.

In some embodiments, a first dimensional position of the incidencephoton in a first direction may be determined based on the first dataset. A second dimensional position of the incidence photon in a seconddirection may be determined based on the second data set. A thirddimensional position of the incidence photon in a third direction may bedetermined based on the first data set and the second data set.

In some embodiments, at least one component of the three-dimensionalposition of the incidence photon in a direction may be related to acoefficient. The coefficient may be a ratio of a sum of the at leastfirst light intensity value in the first data set and a sum of the atleast second light intensity value in the second data set.

In some embodiments, the ratio of the first number of light sensors ofthe first light sensor array to the number of the plurality ofscintillators may be 2 to 1. The ratio of the second number of lightsensors of the second light sensor array to the number of the pluralityof scintillators may be 2 to 1.

In some embodiments, the first number of light sensors of the firstlight sensor array is equal to the second number of light sensors of thesecond light sensor array.

Another aspect of the present disclosure relates to a method fordetermining a three-dimensional position of an incidence photon in aPositron Emission Tomography (PET) system. The method may be implementedon at least one processor and a storage. The method may include one ormore of the following operations. A PET data set corresponding to atarget object may be acquired by the PET system. The three-dimensionalposition of the incidence photon may be determined based on the PET dataset.

A further aspect of the present disclosure relates to a non-transitorycomputer readable medium including executable instructions. Theinstructions, when executed by at least one processor, may cause the atleast one processor to effectuate a method for determining athree-dimensional position of an incidence photon using in a PositronEmission Tomography (PET) system. In some embodiments, thenon-transitory computer readable medium may include instructions forcausing a computer to implement the method described herein.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting exemplaryembodiments, in which like reference numerals represent similarstructures throughout the several views of the drawings, and wherein:

FIG. 1A is a schematic diagram illustrating an exemplary PositronEmission Tomography (PET) system according to some embodiments of thepresent disclosure;

FIG. 1B is a block diagram illustrating an exemplary image processingsystem according to some embodiments of the present disclosure;

FIG. 2 is a block diagram illustrating exemplary hardware and softwarecomponents of a computing device according to some embodiments of thepresent disclosure;

FIG. 3 illustrates a schematic diagram of an exemplary PET scanneraccording to some embodiments of the present disclosure;

FIG. 4 illustrates a schematic diagram of an exemplary detector unitaccording to some embodiments of the present disclosure;

FIG. 5A illustrates a top view of an exemplary scintillator arrayaccording to some embodiments of the present disclosure;

FIG. 5B illustrates a stereogram of an exemplary scintillator arrayaccording to some embodiments of the present disclosure;

FIG. 6A illustrates a top view of an exemplary first light sensor arrayaccording to some embodiments of the present disclosure;

FIG. 6B illustrates a top view of an exemplary second light sensor arrayaccording to some embodiments of the present disclosure;

FIG. 7A illustrates a top view of an exemplary 8×8 scintillator arrayaccording to some embodiments of the present disclosure;

FIG. 7B illustrates a perspective diagram of an exemplary detector unitaccording to some embodiments of the present disclosure;

FIG. 7C illustrates a side view of an exemplary detector unit accordingto some embodiments of the present disclosure;

FIG. 7D illustrates a side view of an exemplary detector unit accordingto some embodiments of the present disclosure;

FIG. 8 illustrates a schematic program of an exemplary processing moduleaccording to some embodiments of the present disclosure;

FIG. 9 illustrates a flow chart of a process for reconstructing an imageof a target object according to same embodiments of the presentdisclosure; and

FIG. 10 illustrates a flow chart of a process for determining athree-dimensional position of an incidence photon according to someembodiments of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present disclosure. Thus, the present disclosure is not limitedto the embodiments shown, but to be accorded the widest scope consistentwith the claims.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise,”“comprises,” and/or “comprising,” “include,” “includes,” and/or“including,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

It will be understood that the term “system,” “unit,” “module,” and/or“block” used herein are one method to distinguish different components,elements, parts, section or assembly of different level in ascendingorder. However, the terms may be displaced by other expression if theyachieve the same purpose.

It will be understood that when a unit, engine, module or block isreferred to as being “on,” “connected to,” or “coupled to,” anotherunit, engine, module, or block, it may be directly on, connected orcoupled to, or communicate with the other unit, engine, module, orblock, or an intervening unit, engine, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

These and other features, and characteristics of the present disclosure,as well as the methods of operation and functions of the relatedelements of structure and the combination of parts and economies ofmanufacture, may become more apparent upon consideration of thefollowing description with reference to the accompanying drawings, allof which form a part of this disclosure. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended to limit thescope of the present disclosure. It is understood that the drawings arenot to scale.

Provided herein are systems and components for non-invasive imaging,such as for disease diagnostic or research purposes. The imaging systemmay find its applications in different fields such as medicine orindustry. For example, the imaging system may be used in internalinspection of components including, for example, flaw detection,security scanning, failure analysis, metrology, assembly analysis, voidanalysis, wall thickness analysis, or the like, or any combinationthereof.

For illustration purposes, the disclosure describes systems and methodsfor determining a three-dimensional position of an incidence photon in aPET system. The PET system may determine the three-dimensional positionof an incidence photon based on a PET data set. As used herein, a PETdata set may refer to a plurality of sub data sets acquired by the PETsystem. For example, the PET data may include a first data setcorresponding to a first direction and a second data set correspondingto a second direction in a three-dimensional coordinate system. Thethree-dimensional position of the incidence photon may be determinedbased on the first data set and the second data set.

The following description is provided to help better understandingmethods or systems for determining a three-dimensional position of anincidence photon. The term “incidence photon” used in this disclosuremay refer to gamma (γ) rays, X rays, etc. The term “three-dimensionalposition” used in this disclosure may refer to a position represented inthree different directions (e.g., in a three-dimensional system). Thedetermination process may be executed by a PET system, a SPECT system,or other imaging system. The determination result may be used forsubsequent image reconstruction in the imaging system. This is notintended to limit the scope the present disclosure. For persons havingordinary skills in the art, a certain amount of variations, changes,and/or modifications may be deducted under guidance of the presentdisclosure. Those variations, changes, and/or modifications do notdepart from the scope of the present disclosure.

FIG. 1A is a schematic diagram illustrating an exemplary PositronEmission Tomography (PET) system according to some embodiments of thepresent disclosure. In some embodiments, the PET system may be amulti-modality system. The exemplary multi-modality system may include acomputed tomography-positron emission tomography (CT-PET) system, amagnetic resonance-positron emission tomography (MR-PET) system, etc. Insome embodiments, the multi-modality imaging system may include modulesand/or components for performing PET imaging and/or related analysis.

The PET system may include a PET scanner 110 and a host computer 120.The PET scanner 110 may include a gantry 111, a detector 112, adetecting region 113, and a subject table 114.

The detector 112 may detect radiation events (e.g., gamma photons)emitted from the detecting region 113. In some embodiments, the detector112 may include a plurality of detector units (e.g., a detector unit 310shown in FIG. 3, a detector unit 315 shown in FIG. 3). The detectorunits may be implemented in any suitable manner, for example, in aring-shape detector, in a rectangle-shape detector, or in an arrayimplemented on any shaped detector. In some embodiments, the pluralityof detector units may be implemented on the detector 112 symmetrically,such as the detector unit 310 and 315 shown in FIG. 3. In someembodiments, the detector unit may include one or more crystal elementsand/or one or more photomultiplier tubes (PMT) (not shown). In someembodiments, a PMT as employed in the present disclosure may be asingle-channel PMT or a multi-channel PMT. The subject table 114 mayposition a subject in the detecting region 113.

In some embodiments, the detected radiation events may be stored orarchived in a storage (e.g., a storage device in the host computer 120),displayed on a display (e.g., a display of or attached to the hostcomputer 120), or transferred to an external storage device (e.g., anexternal storage device attached to the host computer 120 via a cable,or a wired or wireless network). In some embodiments, a user may controlthe PET scanner 110 via the host computer 120.

Further, while not shown, the PET system may be connected to a network(e.g., a telecommunications network, a local area network (LAN), awireless network, a wide area network (WAN) such as the Internet, apeer-to-peer network, a cable network, etc.) for communication purposes.

It should be noted that the above description of the PET system ismerely provided for the purposes of illustration, and not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations and modifications may be madeunder the teachings of the present disclosure. For example, the assemblyand/or function of the PET system may be varied or changed according tospecific implementation scenarios. Merely by way of example, some othercomponents may be added into the PET system, such as a patientpositioning module, a gradient amplifier module, and other devices ormodules. As another example, the storage module 133 may be optional, andthe modules in the PET system may include an integrated storage unitrespectively.

FIG. 1B is a block diagram illustrating an exemplary image processingsystem 100 according to some embodiments of the present disclosure. Theimage processing system 100 may be implemented via the host computer120. As illustrated in FIG. 1B, the image processing system 100 mayinclude an acquisition module 131, a control module 132, a storagemodule 133, a processing module 134, and a display module 135.

The acquisition module 131 may acquire or receive a PET data set. Merelyby way of example, the PET data set may include one or more sub data set(e.g., a first data set described below in connection with in FIG. 7Cand a second data set described below in connection with in FIG. 7D). Insome embodiments, during a PET scan or analysis, a PET tracer may befirst introduced into the subject before a scanning process begins.During the PET scan, the PET tracer may emit positrons, namely theantiparticles of electrons. A positron has the same mass and theopposite electrical charge as an electron, and it undergoes anannihilation (also referred to as an “annihilation event” or a“coincidence event”) with an electron (that may naturally exist inabundance within the subject) as the two particles collide. Anelectron-positron annihilation event (e.g., a positron-electronannihilation event 340 described below in connection with in FIG. 3) mayresult in two 511 keV gamma photons. Upon the generation of the twogamma photons in response to the electron-positron annihilation event,the two gamma photons begin to travel in opposite directions withrespect to one another. The line connecting the two gamma photons may bereferred to as a “line of response (LOR).” The acquisition module 131may obtain the trajectory and/or information of the gamma photons (alsoreferred to as the “PET data set”). For example, the PET data set mayinclude data acquired from the detectors 112 corresponding to the twogamma photons. In some embodiments, the PET data set may be used todetermine three-dimensional positions of the two gamma photons.

In some embodiments, the PET tracer may include carbon (11C), nitrogen(13N), oxygen (15O), fluorine (18F), or the like, or a combinationthereof. Accordingly, in some embodiments, the PET tracer of the presentdisclosure may be organic compounds containing one or more of suchisotopes. These tracers are either similar to naturally occurredsubstances or otherwise capable of interacting with the functionality oractivity of interest within the subject.

The control module 132 may generate one or more control parameters forcontrolling the acquisition module 131, the storage module 133, theprocessing module 134, and/or the display module 135. For example, thecontrol module 132 may control the acquisition module 131 to determineas to whether to acquire a signal, or the time when a signal may beacquired. As another example, the control module 132 may control theprocessing module 134 to select different algorithms to process the PETdata set acquired by the acquisition module 131. In some embodiments,the control module 132 may receive a real-time command provided by auser (e.g., a doctor) or a predetermined command retrieved by a user(e.g., a doctor) from a storage device. The control module 132 mayfurther apply the real-time command or the predetermined command toadjust the acquisition module 131, and/or the processing module 134 totake images of a subject according to the received command. In someembodiments, the control module 132 may communicate with other modulesin the image processing system 100 for exchanging information or data.

The storage module 133 may store the acquired PET data set, the controlparameters, the processed PET data set, or the like, or a combinationthereof. In some embodiments, the storage module 133 may include a massstorage, a removable storage, a volatile read-and-write memory, aread-only memory (ROM), or the like, or any combination thereof. Forexample, the mass storage may include a magnetic disk, an optical disk,a solid-state drives, etc. The removable storage may include a flashdrive, a floppy disk, an optical disk, a memory card, a zip disk, amagnetic tape, etc. The volatile read-and-write memory may include arandom access memory (RAM). The RAM may include a dynamic RAM (DRAM), adouble date rate synchronous dynamic RAM (DDR SDRAM), a static RAM(SRAM), a thyristor RAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc.The ROM may include a mask ROM (MROM), a programmable ROM (PROM), anerasable programmable ROM (PEROM), an electrically erasable programmableROM (EEPROM), a compact disk ROM (CD-ROM), and a digital versatile diskROM, etc. In some embodiments, the storage module 133 may store one ormore programs and/or instructions that may be executed by one or moreprocessors of the image processing system 100 (e.g., the processingmodule 134) to perform exemplary methods described in this disclosure.For example, the storage module 133 may store program(s) and/orinstruction(s) executed by the processor(s) of the image processingsystem 100 to acquire a PET data set, determine a position of anincidence photon, or display any intermediate result or a resultantposition.

The processing module 134 may process information received from modulesin the image processing system 100. In some embodiments, the processingmodule 134 may pre-process the PET data set acquired by the acquisitionmodule 131, or retrieved from the storage module 133. In someembodiments, the processing module 134 may determine three-dimensionalpositions of incidence photons based on the processed PET data set,reconstruct an image based on the determined positions of incidencephotons and the PET data set, generate reports including one or more PETimages and/or other related information, or the like. For example, theprocessing module 134 may process the PET data set based on apre-processing operation including data classification, data screening,data correction (e.g., correction for random coincidences, detectordead-time correction, detector-sensitivity correction), data estimationand subtraction (estimation and subtraction of scattered photons), orthe like, or any combination thereof. As another example, the processingmodule 134 may determine a plurality of pairs of a first data set and asecond data set based on the PET data set corresponding to a pluralityof incidence protons (e.g., gamma protons).

The display module 135 may display any information relating to the imageprocessing system 100. The information may include programs, software,algorithms, data, text, number, images, voice, or the like, or anycombination thereof. In some embodiments, the display module 135 mayinclude a liquid crystal display (LCD), a light emitting diode (LED)based display, a flat panel display, a cathode ray tube (CRT), a touchscreen, or the like, or a combination thereof. The touch screen mayinclude, for example, a resistance touch screen, a capacity touchscreen, a plasma touch screen, a vector pressure sensing touch screen,an infrared touch screen, or the like, or a combination thereof.

In some embodiments, one or more modules illustrated in FIG. 1B may beimplemented in at least part of the exemplary ECT system illustrated inFIG. 1A. For example, the acquisition module 131, the control module132, the storage module 133, the processing module 134, and/or thedisplay module 135 may be integrated into a console. Via the console, auser may set parameters for scanning, control the imaging procedure,control a parameter of the reconstruction of an image, view thereconstructed images, etc. In some embodiments, the console may beimplemented via the host computer 120.

FIG. 2 is a block diagram illustrating exemplary hardware and softwarecomponents of a computing device 200 on which the image processingsystem 100 may be implemented according to some embodiments of thepresent disclosure. In some embodiments, the computing device 200 mayinclude a processor 202, a memory 204, and a communication port 206.

The processor 202 may execute computer instructions (program code) andperform functions of the processing module 134 in accordance withtechniques described herein. Computer instructions may include routines,programs, objects, components, data structures, procedures, modules, andfunctions, which perform particular functions described herein. Forexample, the processor 202 may process the data or information receivedfrom the acquisition module 131, the control module 132, the storagemodule 133, or any other component of the imaging system 100. In someembodiments, the processor 202 may include a microcontroller, amicroprocessor, a reduced instruction set computer (RISC), anapplication specific integrated circuits (ASICs), anapplication-specific instruction-set processor (ASIP), a centralprocessing unit (CPU), a graphics processing unit (GPU), a physicsprocessing unit (PPU), a microcontroller unit, a digital signalprocessor (DSP), a field programmable gate array (FPGA), an advancedRISC machine (ARM), a programmable logic device (PLD), any circuit orprocessor capable of executing one or more functions, or the like, orany combinations thereof. For example, the processor 202 may include amicrocontroller to process the PET data set from the PET scanner 110 fordetermining three-dimensional position of an incidence photon.

The memory 204 may store the data or information received from theacquisition module 131, the control module 132, the storage module 133,the processing module 134, or any other component of the imaging system100. In some embodiments, the memory 204 may include a mass storage, aremovable storage, a volatile read-and-write memory, a read-only memory(ROM), or the like, or any combination thereof. For example, the massstorage may include a magnetic disk, an optical disk, a solid-statedrives, etc. The removable storage may include a flash drive, a floppydisk, an optical disk, a memory card, a zip disk, a magnetic tape, etc.The volatile read-and-write memory may include a random access memory(RAM). The RAM may include a dynamic RAM (DRAM), a double date ratesynchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristorRAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc. The ROM may includea mask ROM (MROM), a programmable ROM (PROM), an erasable programmableROM (PEROM), an electrically erasable programmable ROM (EEPROM), acompact disk ROM (CD-ROM), and a digital versatile disk ROM, etc. Insome embodiments, the memory 204 may store one or more programs and/orinstructions to perform exemplary methods described in the presentdisclosure. For example, the memory 204 may store a program for theprocessing module 134 for determining a three-dimensional position of anincidence photon based on the ECT data set.

The communication port 206 may transmit to and receive information ordata from the acquisition module 131, the control module 132, thestorage module 133, the processing module 134 via network. In someembodiments, the communication port 206 may include a wired port (e.g.,a Universal Serial Bus (USB) port, a High Definition MultimediaInterface (HDMI) port, or the like) or a wireless port (a Bluetoothport, an infrared interface, a WiFi port, or the like).

FIG. 3 illustrates a schematic diagram of an exemplary PET scanner 300according to some embodiments of the present disclosure. The PET scanner300 may be an embodiment of the PET scanner 110 shown in FIG. 1A. ThePET scanner 300 may include a detector ring 320 and a table 330, or thelike.

The detector ring 320 may acquire a PET data set corresponding to atarget object (not shown in FIG. 3). The detector ring 320 may include aplurality of detector units (e.g., a detector unit 310, a detector unit315, etc.). The detector unit 310 and the detector unit 315 may be sameor different type of detector. For example, the detector unit 310 andthe detector 315 may both be block detector. The detector unit 310 andthe detector unit 315 may include a plurality of light sensor elements(e.g., Sx₁ shown in FIG. 7B). The detector unit 310 may detect anincidence photon. The detector unit 310 may be an incidence photondetector, such as a gamma (γ) ray detector. The detector 310 maygenerate detected data (e.g., a first data set detected by a first lightsensor array 410 shown in FIG. 4, a second data set detected by a secondlight sensor array 420 shown in FIG. 4) corresponding to the incidencephoton. The detected data may be used to determine a three-dimensionalposition of the incidence photon.

The table 330 may be used to place a target object (not shown in FIG. 3)for scanning. The target object may be people, an animal, or otherspecies.

In a PET scanning process, a radiopharmaceutical may be administered tothe target object, in which the radioactive decay events of theradiopharmaceutical can produce positrons. A positron may interact withan electron to produce a positron-electron annihilation event 340 thatemits two oppositely directed γ rays 350 and 355 in the oppositedirections (as shown in FIG. 3). Using coincidence detection circuitry(not shown in FIG. 3), the detector ring 320 may detect the coincidentevents corresponding to the positron-electron annihilation event 340.For example, when two γ photons are determined to have been originatedfrom the same positron-electron annihilation event 340, a coincidentevent is detected and a line of response (LOR) is drawn between the twopoints on the respective detectors where the two γ photons weredetected. Further, a two- or three-dimensional image may bereconstructed based on the lines of response. For example, the PETscanner 300 may include multiple detector rings 320 and may allow thecoincidence events to be detected between any two of the multipledetector rings 320 as well as within a single detector ring 320. Whentreating each of the multiple detector rings 320 as a single entity, atwo-dimensional image may be reconstructed individually based on thelines of response detected by each of the multiple detector rings 320.When treating the multiple detector rings 320 as a single entity,three-dimensional images may be reconstructed based on all of the linesof response detected on the multiple detector rings 320. Therefore,distributions of the radiopharmaceutical in the target object may bedetermined based on the two- and/or three-dimensional images.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example, thePET scanner 300 may include a gantry to install the detector ring 320.

FIG. 4 illustrates a schematic diagram of an exemplary detector unit 310according to some embodiments of the present disclosure. The detectorunit 310 may include a multi-layer structure (e.g., a three-layerstructure). The detector unit 310 may include a layer of a first lightsensor array 410, a layer of a scintillator array 420, and a layer of asecond light sensor array 430. In some embodiments, the first lightarray 410 may be attached to an upper plane of the scintillator array420. The second light array 420 may be attached to a lower plane of thescintillator array 420. A three-dimensional coordinate systemcorresponding to the detector unit 310 may be determined (as shown inFIG. 4). Directions of X-axis, Y-axis, and Z-axis may be designated as afirst direction, a second direction and a third direction. The X-Y planeof the three-dimensional coordinate system may be parallel to the upperplane and lower plane of the scintillator array 420. The X-Z plane ofthe three-dimensional coordinate system may be perpendicular to theupper plane and lower plane of the scintillator array 420.

The first light sensor array 410 and/or the second light sensor array430 may be optically coupled with the scintillator array 420. Thescintillator array 420 may generate light when struck by an incidencephoton (e.g., a γ photon). The first light sensor array 410 and thesecond light sensor array 430 may detect the light.

The first light sensor array 410 may generate one or more electricalsignals (e.g., voltage signals, current signals, etc.) based on thedetecting of the light generated in responsive to the incidence photon.The first light sensor array 410 may determine a first data set based onthe one or more electrical signals. Base on the first data set, a lightintensity spatial distribution corresponding to the incidence photon inthe first direction (e.g., X-axis in the three-dimensional coordinatesystem) may be determined.

In some embodiments, the first light sensor array 410 may include aplurality of light sensor elements (e.g., Sx₁, Sx₂, Sx₃, . . . , Sx_(i),. . . ). The plurality of light sensors may be arranged in one or morerows (e.g., row 1, row 2 . . . row M shown in FIG. 6A). Each of theplurality of light sensors in the first light sensor array 410 maydetect the light and generate an electrical signal. A light sensor in arow may connect through an electric circuit to another light sensor(e.g., an adjacent light sensor) in the same row and share a sameelectrical signal collection unit (not shown in FIG. 4). The pluralityof light sensors may not connect to another light sensor in a same rowand each of the plurality of light sensors may have an electrical signalcollection unit (not shown in FIG. 4). With one or more operations, theplurality of light sensors may determine a first data set (e.g., {X₁,X₂, X₃, . . . , X_(i), . . . }) based on the plurality of electricalsignals at a time. The one or more operations may include performing ananalog-to-digital conversion. A datum in the first data set may beacquired by a sensor in the light sensor array 410. For example, X₁ maybe acquired by sensor Sx₁ at a time.

The second light sensor array 430 may generate one or more electricalsignals (e.g., voltage signals, current signals, etc.) based on thedetecting of the light corresponding to the incidence photon. The secondlight sensor 430 may determine a second data set based on the one ormore electricals signals. Based on the second data set, a lightintensity spatial distribution corresponding to the incidence photon inthe second direction (e.g., Y-axis in the three-dimensional coordinatesystem) may be determined.

In some embodiments, the second light sensor array 430 may include aplurality of light sensor elements (e.g., Sy₁, Sy₂, Sy₃, . . . , Sy_(i),. . . ). The plurality of light sensors may be arranged in one or morecolumns (e.g., column 1, column 2 . . . column N shown in FIG. 6B). Eachof the plurality of light sensors in the second sensor array 430 maydetect the light and generate an electrical signal. A light sensor in acolumn may connect through an electric circuit to another light sensor(e.g., an adjacent light sensor) in the same column and share a sameelectrical signal collection unit (not shown in FIG. 4). The pluralityof light sensors may not connect to another light sensor in a samecolumn and each of the plurality of light sensors may have an electricalsignal collection unit (not shown in FIG. 4). With one or moreoperations, the plurality of light sensors may determine a second dataset (e.g., {Y₁, Y₂, Y₃, . . . , Y_(i), . . . }) based on the pluralityof electrical signals at a time. The one or more operations may includeperforming an analog-to-digital conversion. A datum in the second dataset may be acquired by a sensor in the second light sensor array 430.For example, Y₁ may be acquired by sensor Sy₁.

Light sensors in the first light sensor array 410 and the second lightsensor array 430 may be same or different type of detector. The lightsensors may include silicon photomultipliers (SiPMs), avalanchedphotodiodes (APDs), photomultiplier tubes (PMTs), etc. The light sensorsin the first light sensor array 410 and the second light sensor array430 may be arranged uniformly or ununiformly in their separationdistance, sensor number density, or the like. For example, a separationdistance of each two adjacent light sensors in the first light sensor410 and the second light sensor array 430 may be same. As anotherexample, a number of light sensors in each of the first light sensorarray 410 and the second light sensor array 430 in the first direction(e.g., X-axis in the three-dimensional coordinate system) and the seconddirection (e.g., Y-axis in the three-dimensional coordinate system) maybe same. A number of the light sensors in the first light sensor array410 and a number of the light sensors in the second light sensor array430 may be the same or different.

The scintillator array 420 may include one or more scintillators (i.e.,scintillator elements). The scintillators may be arranged in one or morerows (e.g., K rows shown in FIG. 5A) and one or more columns (e.g., Pcolumns shown in FIG. 5B). The scintillators may further be arranged inone or more layers. The scintillators may be used to record ionizingradiation (e.g., γ rays). In the PET scanner 300, the radiation may begenerated by the annihilation of positrons emitted by an administeredradiopharmaceutical. For example, when a scintillator receives a γphoton, the γ photon may travel a certain distance within thescintillator before it is finally absorbed by the scintillator. Thedistance is known as the depth of interaction (DOI). At the positionwhere the γ photon is absorbed, the scintillator may convert a fractionof the absorbed energy into visible or ultraviolet photons. Theconversion process may produce a pulse of light corresponding to each γphoton that interacts with the scintillator. An intensity of the pulseof light is usually proportional to the energy deposited in thescintillator.

The scintillators in the scintillator array 420 may be any type ofscintillator with one or more physical properties and/or scintillationproperties (e.g., intensity, effective atomic number, decay time, lightoutput, emission wave length, energy resolution, transparent at emissionwavelength, index of refraction, radiation hard, nonhygroscopic, rugged,and economic growth process, etc.). For example, the intensity of thescintillator in the scintillator array 420 may be from 3.00 g/cm³ to 10g/cm³. For another example, the effective atomic number of thescintillator in the scintillator array 420 may be from 10 to 100. Asanother example, the emission wave length of the emission wave lengthmay be near 400 nm. Exemplary materials suitable for the scintillatorsin the scintillator array 410 may include sodium iodide (NaI), cesiumiodide (CsI), lanthanum bromide (LaBr₃), lanthanum chloride (LaCl₃),lutetium oxyorthosilicate (Lu₂SiO₅), lutetium yttrium orthosilicate(LYSO), lutetium pyrosilicate, bismuth germinate (BGO), gadoliniumorthosilicate (GSO), lutetium gadolinium orthosilicate, barium fluoride(BaF₂), yttrium aluminate (YAlO₃), or the like, or any combinationthereof.

The scintillators in the scintillator array 410 may be in multipleshapes. For example, the scintillators may be in a shape of sphere,cuboid, rod, wire, ramp, columns or disks with various cross-sectionalshapes, or the like, or a combination thereof. The scintillators may beliquid or solid, organic or inorganic, and crystalline ornon-crystalline. Herein taking a crystalline structure as an example,the crystalline structure may include a single-layer crystal and amultilayer crystal. The single-layer crystal may include only one layerof crystal. The multilayer crystal may comprise more than one layer ofcrystal. The scintillators in the scintillator array 410 may be indifferent sizes. Different sizes of the scintillator may correspond todifferent energy resolution levels. There may be a particular size inwhich the scintillators demonstrate an optimal energy resolution. Thescintillators in the scintillator array 410 may be arranged uniformly orununiformly in their separation distance, scintillator number density,or the like. For example, a separation distance of each two adjacentscintillators may be same. As another example, scintillator numberdensity in a first area of the scintillator array 410 (e.g., an areafrom column 1 to column 3) and scintillator number density of a secondarea of the scintillator array 410 (e.g., an area from column 11 tocolumn 13) may be different.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example, thedetector unit 310 may include one or more light guides and/orcollimators between the first light sensor array 410 and thescintillator array 420 for guiding the light emitted from thescintillator array 420 to the first light sensor array 410.

FIG. 5A illustrates a top view of an exemplary scintillator array 420according to some embodiments of the present disclosure. The top view isa view of the X-Y plane of the scintillator array 420. As shown in FIG.5A, the scintillator array 420 may include a plurality of scintillators.

The scintillator array 420 may be a single-layer array or a multi-layerarray. When the scintillator array 420 is a single-layer array with Krows and P columns, a number of scintillator elements (e.g.,scintillators) in the scintillator array 420 may be determined based onthe rows and columns (e.g., K×P). K and P may be any positive integer(e.g., 1, 2, 3, 6, 8, and 10, etc.). K and P may be the same ordifferent. When the scintillator array 420 is a multi-layer array with Krows, P columns and Q layers, a number of scintillators in thescintillator array 420 may be determined based on the rows, columns andlayers (e.g., K×P×Q).

FIG. 5B illustrates a stereogram of an exemplary scintillator array 420according to some embodiments of the present disclosure. FIG. 5B uses asingle-layer array merely for the purpose of illustration. In someembodiments, the scintillator array 420 may also be a multi-layer array.As shown in FIG. 5B, a number of column of the scintillator array 420may be P and a number of row of the scintillator array 420 may be K.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example, theremay be gap spacings between the scintillators in the scintillator array420. The gap spacings may be filled with a conductive or non-conductivematerial for shielding the scintillators from external electric fieldinterference.

FIG. 6A illustrates a top view of an exemplary first light sensor array410 according to some embodiments of the present disclosure. The topview is a view of the X-Y plane of the first light sensor array 410. Thefirst light sensor array 410 may be in a layer that is parallel to theX-Y plane. The first light sensor array 410 may include a plurality oflight sensors arranged in M rows. The M rows may be parallel to thefirst direction (e.g., X-axis in the three-dimensional coordinatesystem). Light sensors in a row (e.g., a light sensor S_(x2) and a lightsensor S_(x3) in Row 1) may connect to another light sensor (e.g., anadjacent light sensor) through an electric circuit and share a sameelectrical signal collection unit (not shown in FIG. 4). For example,the light sensor S_(x2) may connect to the light sensor S_(x3). Asanother example, the light sensor S_(x1) may connect to the light sensorS_(x3).

FIG. 6B illustrates a top view of an exemplary second light sensor array430 according to some embodiments of the present disclosure. The topview is a view of the X-Y plane of the second light sensor array 430.The second light sensor array 430 may be in a layer that is parallel tothe X-Y plane. The second light sensor array 430 may include a pluralityof light sensors arranged in N columns. The N columns may be parallel tothe second direction (e.g., Y-axis in the three-dimensional coordinatesystem).

In some embodiments, both the number of the plurality of light sensorsin the first light sensor array 410 and the number of the plurality oflight sensors in the second light sensor array 430 may be less than thenumber of the scintillators in the scintillator array 420. For example,when the scintillator array 420 includes 16 scintillators, both of thefirst light sensor array 410 and the second light sensor array 430 mayinclude any number of light sensors that are less than 16 (e.g., 8, 4,etc.). In some embodiments, the number of the plurality of light sensorsin the first light sensor array 410 and the number of the plurality oflight sensors in the second light sensor array 430 may be the same ordifferent. For example, in a detector unit 310 with a 4×4 scintillatorarray 420, the first light sensor array 410 and the second light sensorarray 420 may include different numbers of light sensors, e.g., fourlight sensors in the first light sensor array 410 and eight lightsensors in the second light sensor array 420. As another example, in adetector unit 310 with a 4×4 scintillator array 420, the first lightsensor array 410 and the second light sensor array 420 may include thesame numbers of light sensors, e.g., four light sensors in the firstlight sensor array 410 and four light sensors in the second light sensorarray 420, or eight light sensors in the first light sensor array 410and eight light sensors in the second light sensor array 420.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. For example, gapspacings between light sensors in the first light sensor array 410 maybe uniform or non-uniform. For example, a gap spacing between lightsensor Sx₁ and light sensor Sx₂ may be 0.19 nm and a gap spacing betweenlight sensor Sx₂ and light sensor Sx₃ may be 0.15 nm.

FIG. 7A illustrates a top view of an exemplary 8×8 scintillator array710 according to some embodiments of the present disclosure. The topview is a view of the X-Y plane of the 8×8 scintillator array 710. The8×8 scintillator array 710 may be an embodiment of the scintillatorarray 420 shown in FIG. 4.

FIG. 7B illustrates a perspective diagram of an exemplary detector unit720 according to some embodiments of the present disclosure. Thedetector unit 720 may be an embodiment of the detector unit 310 shown inFIG. 4. FIG. 7B shows a perspective diagram of an exemplary detectorunit 720 from a top view. The detector unit 720 may include an a firstlight sensor array 721, the 8×8 scintillator array 710, a second lightsensor array (not shown in FIG. 7B). The first light sensor array 721and the second light sensor array (not shown in FIG. 7B) may have thesame number of light sensors (e.g., 4 light sensors). The second lightsensor array may not be illustrated as it is beneath the first lightsensor array 721 in FIG. 7B.

The first light sensor array 721 may include a light sensor Sx₁, a lightsensor Sx₂, a light sensor Sx₃ and a light sensor Sx₄. The light sensorSx₁ and the light sensor Sx₃ may be in a first row of the first lightsensor array 721. The light sensor Sx₂ and the light sensor Sx₄ may bein a second row of the first light sensor array 721.

The first light sensor array 721 may be configured to acquire a firstdata set (e.g., {X₁, X₂, X₃, and X₄}) based on the light sensors Sx₁,Sx₂, Sx₃ and Sx₄. The imaging processing system 100 may determine alight intensity spatial distribution corresponding to an incidencephoton in the first direction (e.g., X-axis in the three-dimensionalcoordinate system).

FIG. 7C illustrates a side view of the exemplary detector unit 720according to some embodiments of the present disclosure. FIG. 7C may bea side view of the Y-Z plane of the detector unit 720. Only Sx₁ of thetwo light sensors Sx₁ and Sx₃ in the first row of the first light sensorarray 721 may be shown in FIG. 7C. The side view of the Y-Z plane of thedetector unit 720 only shows the light sensor Sx₁, and the light sensorSx₃ may be behind the light sensor Sx₁. Only Sx₂ of the two lightsensors Sx₂ and Sx₄ in the second row of the first light sensor array721 may be shown in FIG. 7C. The light sensor Sx₄ may be behind thelight sensor Sx₂.

FIG. 7D illustrates a side view of the exemplary detector unit 720according to some embodiments of the present disclosure. FIG. 7D may bea view of the X-Z plane of the detector unit 720.

The second light sensor array 722 may include a light sensor Sy₁, alight sensor Sy₂, a light sensor Sy₃ and a light sensor Sy₄. The lightsensor Sy₁ and the light sensor Sy₃ may be in a first column of thefirst light sensor array 722. The light sensor Sy₂ and the light sensorSy₄ may be in a second column of the second light sensor array 722. OnlySy₁ of the two light sensors Sy₁ and Sy₃ in the first column of thesecond light sensor array 722 may be shown in FIG. 7D. The light sensorSy₃ may be behind the light sensor Sy₁. Only Sy₂ of the two lightsensors Sy₂ and Sy₄ in the second column of the second light sensorarray 722 may be shown in FIG. 7D. The light sensor Sy₄ may be behindthe light sensor Sy₂.

The second light sensor array 722 may be configured to acquire a seconddata set (e.g., {Y₁, Y₂, Y₃, and Y₄}) based on the light sensors Sy₁,Sy₂, Sy₃ and Sy₄. The imaging processing system 100 may determine alight intensity spatial distribution corresponding to an incidencephoton in the second direction (e.g., Y-axis in the three-dimensionalcoordinate system) based on the second data set.

FIG. 8 illustrates a schematic program of an exemplary processing module134 according to some embodiments of the present disclosure. Asillustrated in FIG. 8, the processing module 134 may include a datapre-processing unit 810, a position determination unit 820, an imagereconstruction unit 830, etc.

The data pre-processing unit 810 may be configured to pre-process a PETdata set. The pre-processing the PET data set may include dataclassification, data screening, data correction (e.g., correction forrandom coincidences, detector dead-time correction, detector-sensitivitycorrection), data estimation and subtraction (estimation and subtractionof scattered photons), or the like, or any combination thereof. Thepre-processed data set may include multiple sub data sets. In someembodiments, the PET data set and/or the pre-processed data set may bestored in the storage module 133.

The position determination unit 820 may be configured to determinethree-dimensional position of an incidence photon corresponding to atarget object. The three-dimensional position of the incidence photonmay be determined based on the pre-processed data set. The positiondetermination unit 820 may be configured to may determine a position ofan annihilation event. The position of an annihilation event may bedetermined based on the positions of a pair of incidence photons.

The image reconstruction unit 830 may be configured to reconstruct animage of the target object. The image may be reconstructed based on thethree-dimensional positions of the incidence photon and the PET dataset. The image may be a two-dimensional image or a three-dimensionalimage. In some embodiments, the image may be displayed on a display ofthe display module 135.

It should be noted that the descriptions above in relation to theprocessing module 134 is provided for the purposes of illustration, andnot intended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, various variations and modificationsmay be conducted under the guidance of the present disclosure. However,those variations and modifications do not depart the scope of thepresent disclosure. For example, the processing module 134 may include astorage unit (no shown in FIG. 8) to store the pre-processed PET data.Similar modifications should fall within the scope of the presentdisclosure.

FIG. 9 illustrates a flow chart of a process for reconstructing an imageof a target object according to same embodiments of the presentdisclosure. The target object may be a patient that is administered aradiopharmaceutical. The suitability of the radiopharmaceutical maydepend, in part, upon the organs or tissues of the target object to beimaged. The radiopharmaceutical may cause an annihilation event (thepositron-electron annihilation event 340) that emits a pair of incidencephotons (e.g., γ photons) in opposite directions or nearly oppositedirections (close to 180°). A pair of detector units (e.g., the detectorunit 310 and the detector unit 315) that are placed 180° from each othermay detect the pair of incidence photons emitted from a singleannihilation event (e.g., the positron-electron annihilation event 340).In some embodiments, a PET system may include more than one pair ofdetector units and more than one annihilation events. Herein below, apair of detector units and an annihilation event may be taken as anexample in descriptions of the following steps of FIG. 9. The process900 may be executed by the imaging processing system 100 shown in FIG.1B. Process 900 may be performed by the imaging processing system 100shown in FIG. 1B. One or more operations of process 900 may be performedby the computing device 200.

In 910, the imaging processing system 100 may acquire a PET data setcorresponding to the target object. In some embodiments, step 910 may beexecuted by the acquisition module 131 shown in FIG. 1B.

The PET data set may include a plurality of sub data sets acquired bythe acquisition module 131 (e.g., a first data set acquired by thedetected unit 310, a second data set acquired by the detected unit 315,etc.). The PET data set may include some other data (e.g., informationrelated to the target object) required in an image reconstruction.

In 920, the imaging processing system 100 may pre-process the PET dataset. A pre-processed data set may be generated based on thepre-processing operation. In some embodiments, step 920 may be executedby the data pre-processing unit 810 shown in FIG. 8.

The pre-processing of the PET data set may include data classification,data screening, data correction (e.g., correction for randomcoincidences, detector dead-time correction, detector-sensitivitycorrection), data estimation and subtraction (estimation and subtractionof scattered photons), or the like, or any combination thereof.

In some embodiments, a first data set and a second data setcorresponding to the positron-electron annihilation event 340 of anincidence photon may be determined as a pre-processed data set. The twodata sets may be acquired by a pair of detector units (e.g., thedetected unit 315 and the detected unit 310) placed 180° from each otherin a given time window. For example, the first data set may be {X₁, X₂,X₃, and X₄} described above in connection with FIG. 7C, and the seconddata set may be {Y₁, Y₂, Y₃, and Y₄} described above in connection within FIG. 7D.

In 930, the imaging processing system 100 may determine athree-dimensional position of at least one incidence photoncorresponding to the target object. In some embodiments, step 930 may beexecuted by the position determination unit 820 shown in FIG. 8.

The three-dimensional position of the at least one incidence photon maybe determined based on the pre-processed data set. In some embodiments,the three-dimensional position of the at least one incidence photon maybe determined based on the first data set (e.g., {X₁, X₂, X₃, and X₄})and the second data set (e.g., {Y₁, Y₂, Y₃, and Y₄}). Details ofdetermining the three-dimensional position of the at least one incidencephoton may be found in FIG. 10, and descriptions thereof.

In 940, the imaging processing system 100 may reconstruct an image ofthe target object based on the three-dimensional positions of the pairof the incidence photons and the PET data set. In some embodiments, step930 may be executed by the image reconstruction unit 830.

Based on the three-dimensional positions of the pair of incidencephotons, a line of response may be determined between the two positionson the pair of detectors. A position of the annihilation event (e.g.,the positron-electron annihilation event 340) may be in the line ofresponse. Such lines of response may be used for reconstruction of animage. The image may be two-dimensional or three-dimensional. Forexample, based on lines of response corresponding to a single detectorring 320, a two-dimensional image may be reconstructed. Athree-dimensional image may be reconstructed based on all of the linesof response detected on the pairs of detector units of multiple detectorrings 320. In some embodiments, the position of the annihilation eventmay be calculated based on the difference between a time of flight (TOF)of the pair of incidence photons and the lines of response.

One or more techniques may be used in the image reconstructing, forexample, a filtered back projection (FBP) technique, a statistical,likelihood-based approaches technique, an attenuation correctiontechnique, or the like, or any combination thereof.

It should be noted that process 900 described above is provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. Apparently for persons having ordinary skills in theart, numerous variations and modifications may be conducted under theteaching of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For instance, an image combination operation (e.g., combination of PETwith CT) may be performed after the image reconstruction. Similarmodifications should fall within the scope of the present disclosure.

FIG. 10 illustrates a flow chart of a process 1000 for determining athree-dimensional position of an incidence photon according to someembodiments of the present disclosure. Process 1000 may be performed bythe imaging processing system 100 shown in FIG. 1B. One or moreoperations of process 1000 may be performed by the computing device 200.In some embodiments, process 1000 described with reference to FIG. 8 maybe an exemplary process for achieving 930 shown in FIG. 9.

In 1010, the imaging processing system 100 may determine a first dataset corresponding to an incidence photon detected by a first lightsensor array.

In some embodiments, the first data set may be data set {X₁, X₂, X₃, andX₄} as described above in connection with FIG. 7C. The data in the firstdata set may correspond to a light intensity of a light detected bylight sensors of the first light sensor array 721. The light may begenerated by the scintillator in the 8×8 scintillator array 710corresponding to the incidence photon.

In 1020, the imaging processing system 100 may determine a second dataset corresponding to the incidence photon detected by a second lightsensor array.

In some embodiments, the second data set may be data set {Y₁, Y₂, Y₃,and Y₄} as described above in connection with FIG. 7D. The data in thesecond data set may correspond to the light intensity of the lightdetected by light sensors of a second light sensor array 722. The lightmay be generated by the scintillator in the 8×8 scintillator array 710corresponding to the incidence photon.

In 1030, the imaging processing system 100 may determine a firstdimensional position of the incidence photon in the first directionbased on the first data set. The first dimensional position may refer toa position in the first direction (e.g., X-axis in the three-dimensionalcoordinate system). The first dimensional position of the incidencephoton may be determined based on a first light intensity spatialdistribution corresponding to the incidence photon. The first lightintensity spatial distribution may be determined based on the first dataset.

In some embodiments, the first light intensity spatial distribution maybe determined based on data in the first data set. For example, thefirst data set may be {X₁, X₂, X₃, and X₄} and the first dimensionalposition x may be determined by equation (1):x=X ₁ +X ₃/(X ₁ +X ₂ +X ₃ +X ₄).  (1)

In 1040, the imaging processing system 100 may determine a seconddimensional position of the incidence photon in the second directionbased on the second data set. The second dimensional position may referto a position in the second direction (e.g., Y-axis in thethree-dimensional coordinate system). The second dimensional position ofthe incidence photon may be determined based on a second light intensityspatial distribution corresponding to the incidence photon. The secondlight intensity spatial distribution may be determined based on thesecond data set.

In some embodiments, the second light intensity spatial distribution maybe determined based on data in the second data set. For example, thesecond data set may be {Y₁, Y₂, Y₃, and Y₄} and the second dimensionalposition y may be determined by equation (2):y=Y ₁ +Y ₃/(Y ₁ +Y ₂ +Y ₃ +Y ₄).  (2)

In 1050, the imaging processing system 100 may determine a thirddimensional position of the incidence photon in a third direction basedon the first data set and the second data set. The third dimensionalposition may refer to a position in the third direction (e.g., Z-axis inthe three-dimensional coordinate system). The third dimensional positionof the incidence photon may be determined based on a third lightintensity spatial distribution corresponding to the incidence photon.The third light intensity spatial distribution may be determined basedon the first data set and the second data set.

In some embodiments, the third light intensity spatial distribution maybe determined based on a coefficient. The coefficient may be a ratio ofa sum of the at least first light intensity value in the first data setand a sum of the at least second light intensity value in the seconddata set. For example, the coefficient C_(z) may be determined byequation (3):C _(z)=(X ₁ +X ₂ +X ₃ +X ₄)/(X ₁ +X ₂ +X ₃ +X ₄ +Y ₁ +Y ₂ +Y ₃ +Y₄).  (3)

Then the third dimensional position Z may be determined based on C_(z).For example, Z may be determined by a product of C_(z) and a thicknessof the scintillator in the 8×8 scintillator array 710.

Therefore, the three-dimensional position of the incidence photon in thethree-dimensional coordinate system may be determined based on the firstdimensional position, the second dimensional position and the thirddimensional position of the incidence photon. Based on positions ofincidence photons, one or more parameters (e.g., a line of response, adepth of interaction, a position of an annihilation event, etc.) may bedetermined for image reconstruction.

It should be noted that process 1000 described above is provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. Apparently for persons having ordinary skills in theart, numerous variations and modifications may be conducted under theteaching of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For instance, a coordinate conversion operation may be performed afterthe determination of the three-dimensional position of the incidencephoton in order to describe more than one incidence photons in a samecoordinate. Similar modifications should fall within the scope of thepresent disclosure.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and/or “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art, aspects ofthe present disclosure may be illustrated and described herein in any ofa number of patentable classes or context including any new and usefulprocess, machine, manufacture, or composition of matter, or any new anduseful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “block,” “module,” “engine,” “unit,” “component,” or“system.” Furthermore, aspects of the present disclosure may take theform of a computer program product embodied in one or more computerreadable media having computer readable program code embodied thereon.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including electro-magnetic, optical, or thelike, or any suitable combination thereof. A computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that may communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device. Program code embodied on acomputer readable signal medium may be transmitted using any appropriatemedium, including wireless, wireline, optical fiber cable, RF, or thelike, or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C #, VB.NET, Python or the like, conventional procedural programming languages,such as the “C” programming language, Visual Basic, Fortran 2003, Perl,COBOL 2002, PHP, ABAP, dynamic programming languages such as Python,Ruby and Groovy, or other programming languages. The program code mayexecute entirely on the operator's computer, partly on the operator'scomputer, as a stand-alone software package, partly on the operator'scomputer and partly on a remote computer or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the operator's computer through any type of network,including a local area network (LAN) or a wide area network (WAN), orthe connection may be made to an external computer (for example, throughthe Internet using an Internet Service Provider) or in a cloud computingenvironment or offered as a service such as a Software as a Service(SaaS).

Furthermore, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations therefore, is notintended to limit the claimed processes and methods to any order exceptas may be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful embodiments of the disclosure, it is to be understoodthat such detail is solely for that purpose, and that the appendedclaims are not limited to the disclosed embodiments, but, on thecontrary, are intended to cover modifications and equivalentarrangements that are within the spirit and scope of the disclosedembodiments. For example, although the implementation of variouscomponents described above may be embodied in a hardware device, it mayalso be implemented as a software only solution—e.g., an installation onan existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the present disclosure, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure aiding in theunderstanding of one or more of the various inventive embodiments. Thismethod of disclosure, however, is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, inventive embodiments liein less than all features of a single foregoing disclosed embodiment.

What is claimed is:
 1. A Positron Emission Tomography (PET) system foracquiring a PET data set of a target object, comprising: a scintillatorarray having a plurality of scintillators arranged in multiple rows andmultiple columns; a first light sensor array having a first number oflight sensors arranged in one or more rows, wherein one light sensor ina row connects through an electric circuit to an adjacent light sensorin the same row and shares a same electrical signal collection unit; anda second light sensor array having a second number of light sensorsarranged in one or more columns, wherein one light sensor in a columnconnects through an electric circuit to an adjacent light sensor in thesame column and shares a same electrical signal collection unit, whereina first surface of the scintillator array is optically coupled to thefirst light sensor array and a second surface of the scintillator arrayis optically coupled to the second light sensor array, and ascintillator number density in a first area of the scintillator arrayand a scintillator number density in a second area of the scintillatorarray are different.
 2. The PET system of claim 1, wherein at least onelight sensor of the first light sensor array is optically coupled to atleast two rows and at least two columns of scintillators of thescintillator array.
 3. The PET system of claim 1, wherein the firstnumber of light sensors of the first light sensor array or the secondnumber of light sensors of the second light sensor array is less thanthe number of the plurality of scintillators.
 4. The PET system of claim1, wherein at least one light senor in the first light sensor array orthe second light sensor array comprises a silicon photomultiplier(SiPM).
 5. The PET system of claim 1, wherein the PET data set comprisesa first data set comprising at least a first light intensity valuecorresponding to an incidence photon detected by the first light sensorarray, and a second data set comprising at least a second lightintensity value corresponding to an incidence photon detected by thesecond sensor array.
 6. The PET system of claim 5, wherein a firstdimensional position of the incidence photon in a first direction isdetermined based on the first data set; a second dimensional position ofthe incidence photon in a second direction is determined based on thesecond data set; and a third dimensional position of the incidencephoton in a third direction is determined based on the first data setand the second data set.
 7. The PET system of claim 5, wherein at leastone component of a three-dimensional position of the incidence photon ina direction relates to a coefficient, the coefficient being a ratio of asum of the at least first light intensity value in the first data set toa sum of the at least second light intensity value in the second dataset.
 8. The PET system of claim 1, wherein a ratio of the first numberof light sensors of the first light sensor array to the number of theplurality of scintillators is 2 to 1, and a ratio of the second numberof light sensors of the second light sensor array to the number of theplurality of scintillators is 2 to
 1. 9. The PET system of claim 1,wherein the first number of light sensors of the first light sensorarray is equal to the second number of light sensors of the second lightsensor array.
 10. The PET system of claim 1, wherein the first number oflight sensors of the first light sensor array and the second number oflight sensors of the second light sensor array are arranged uniformly orununiformly.
 11. The PET system of claim 1, wherein the first number oflight sensors of the first light sensor array and the second number oflight sensors of the second light sensor array are arranged according toa separation distance or according to a sensor number density.
 12. ThePET system of claim 1, wherein the plurality of scintillators arearranged uniformly or ununiformly.
 13. The PET system of claim 1,wherein the plurality of scintillators are arranged according to aseparation distance.
 14. A method for determining a three-dimensionalposition of an incidence photon in a Positron Emission Tomography (PET)system, the method implemented on at least one processor and a storageand comprising: acquiring a PET data set corresponding to a targetobject; and determining the three-dimensional position of the incidencephoton based on the PET data set, wherein the PET system comprises afirst light sensor array having a first number of light sensors arrangedin one or more rows, a second light sensor array having a second numberof light sensors arranged in one or more columns, and a scintillatorarray having a plurality of scintillators arranged in multiple rows andmultiple columns, wherein one light sensor in a row connects through anelectric circuit to an adjacent light sensor in the same row and sharesa same electrical signal collection unit, one light sensor in a columnconnects through an electric circuit to an adjacent light sensor in thesame column and shares a same electrical signal collection unit, thefirst light sensor array is optically coupled to a first surface of thescintillator array, the second light sensor array is optically coupledto a second surface of the scintillator array, and a scintillator numberdensity in a first area of the scintillator array and a scintillatornumber density in a second area of the scintillator array are different.15. The method of claim 14, further comprising: reconstructing an imageof the target object based on the three-dimensional position of theincidence photon and the PET data set.
 16. The method of claim 15,further comprising: determining, based on a light intensity spatialdistribution corresponding to the incidence photon in a direction, atleast one component of the three-dimensional position of the incidencephoton in the direction.
 17. The method of claim 14, wherein the PETdata set comprises a first data set comprising at least a first lightintensity value corresponding to the incidence photon detected by thefirst light sensor array, and a second data set comprising at least asecond light intensity value corresponding to the incidence photondetected by the second sensor array.
 18. The method of claim 17, furthercomprising: determining, based on the first data set, a firstdimensional position of the incidence photon in a first direction;determining, based on the second data set, a second dimensional positionof the incidence photon in a second direction; and determining, based onthe first data set and the second data set, a third dimensional positionof the incidence photon in a third direction.
 19. A non-transitorycomputer readable medium comprising executable instructions that, whenexecuted by at least one processor, cause the at least one processor toeffectuate a method for determining a three-dimensional position of anincidence photon in a Positron Emission Tomography (PET) system, themethod comprising: acquiring a PET data set corresponding to a targetobject; and determining the three-dimensional position of the incidencephoton based on the PET data set, wherein the PET system comprises afirst light sensor array having a first number of light sensors arrangedin one or more rows, a second light sensor array having a second numberof light sensors arranged in one or more columns, and a scintillatorarray having a plurality of scintillators arranged in multiple rows andmultiple columns, wherein one light sensor in a row connects through anelectric circuit to an adjacent light sensor in the same row and sharesa same electrical signal collection unit, one light sensor in a columnconnects through an electric circuit to an adjacent light sensor in thesame column and shares a same electrical signal collection unit, thefirst light sensor array is optically coupled to a first surface of thescintillator array, the second light sensor array is optically coupledto a second surface of the scintillator array, and a scintillator numberdensity in a first area of the scintillator array and a scintillatornumber density in a second area of the scintillator array are different.20. The non-transitory computer readable medium of claim 19, wherein thePET data set comprises a first data set comprising at least a firstlight intensity value corresponding to the incidence photon detected bythe first light sensor array, and a second data set comprising at leasta second light intensity value corresponding to the incidence photondetected by the second sensor array.